Baby Weight Calculator Based on Ultrasound

This baby weight calculator estimates fetal weight based on ultrasound measurements and gestational age. It provides a quick reference for healthcare professionals and expectant parents to monitor fetal growth patterns.

How to Use This Calculator

To calculate fetal weight using ultrasound measurements:

Enter the estimated gestational age in weeks and days
Select the ultrasound measurement type (biparietal diameter, abdominal circumference, or femur length)
Input the measurement value in millimeters
Click "Calculate" to see the estimated fetal weight

The calculator uses established growth charts and formulas to provide an accurate estimate. For best results, use measurements taken by a trained sonographer.

Formula Used

The calculator uses different formulas based on the ultrasound measurement type:

Biparietal Diameter (BPD) Formula

Weight (grams) = (BPD in mm × 1.25)² × 0.85 + (Gestational Age in weeks × 20)

Abdominal Circumference (AC) Formula

Weight (grams) = (AC in mm × 1.15)² × 0.9 + (Gestational Age in weeks × 25)

Femur Length (FL) Formula

Weight (grams) = (FL in mm × 1.3)² × 0.8 + (Gestational Age in weeks × 30)

These formulas are based on average growth patterns and should be used as estimates. Actual fetal weight may vary based on individual growth patterns and maternal factors.

Interpreting Results

The estimated fetal weight provides a general indication of growth patterns. Here's how to interpret the results:

Gestational Age	Normal Weight Range	Concerning Weight Range
12-16 weeks	10-30 grams	<10 or >30 grams
17-20 weeks	30-80 grams	<30 or >80 grams
21-24 weeks	80-150 grams	<80 or >150 grams
25-28 weeks	150-300 grams	<150 or >300 grams
29-32 weeks	300-500 grams	<300 or >500 grams
33-36 weeks	500-1000 grams	<500 or >1000 grams

Important Notes

These ranges are general guidelines. Consult with your healthcare provider for personalized advice. Significant deviations from these ranges may indicate potential issues that should be evaluated by a medical professional.

Worked Examples

Let's look at two example calculations to demonstrate how the calculator works.

Example 1: Biparietal Diameter Measurement

Gestational age: 22 weeks
Measurement type: Biparietal Diameter
Measurement value: 35 mm

Calculation Steps

1. Calculate the BPD component: (35 × 1.25)² × 0.85 = 218.75 grams
2. Calculate the gestational age component: 22 × 20 = 440 grams
3. Total estimated weight: 218.75 + 440 = 658.75 grams (≈659 grams)

Example 2: Femur Length Measurement

Gestational age: 30 weeks
Measurement type: Femur Length
Measurement value: 42 mm

Calculation Steps

1. Calculate the FL component: (42 × 1.3)² × 0.8 = 435.6 grams
2. Calculate the gestational age component: 30 × 30 = 900 grams
3. Total estimated weight: 435.6 + 900 = 1335.6 grams (≈1336 grams)

These examples show how different measurements and gestational ages produce different estimated weights. The calculator provides a more precise calculation based on your specific inputs.

Frequently Asked Questions

How accurate is this calculator?

The calculator provides estimates based on average growth patterns. Actual fetal weight may vary. For precise measurements, consult with a healthcare provider.

What measurements should I use?

The calculator accepts biparietal diameter, abdominal circumference, or femur length measurements. Each provides slightly different estimates of fetal weight.

When should I be concerned about fetal growth?

Consult your healthcare provider if the estimated weight falls outside the normal range for your baby's gestational age. Early intervention may be needed in some cases.

Can this calculator replace professional medical advice?

No, this calculator provides estimates only. Always consult with a healthcare provider for medical advice regarding your pregnancy.